<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        //int num
        //js
        var v;
        console.log(v);
        console.log(typeof (v));
        v=3.14;
        console.log(v);
        console.log(typeof (v));
        v='hello js';
        console.log(v);
        console.log(typeof (v));
        v =true;
        console.log(v);
        console.log(typeof (v));
        v=null;
        console.log(v);
        console.log(typeof (v));
    </script>
</head>
<body>

</body>
</html>